//
// Created by 123 on 2025/1/7.
//
#include "iostream"
#include "string"
using namespace std;


int main117(){
    string str = "31111";
    str.insert(1,"22");
    cout << str << endl;
    str.erase(1,3);
    cout << str << endl;

    string s = "hello@sina.com";
    int pos = s.find("@");
    string name = s.substr(0,pos);
    cout << "name=" << name << endl;

    return 0;
}